Germany's submarine warfare was unrestricted. These attacks led to World War I.
Submarine warfare is a military tactic used by many nations where submarines are used to attack enemy ships or as a direct deterrent. This was used extensively by the Germans during World War II.
We warned them not to return to "un-restricted warfare." They did it anyway; we declared war.
The use of airplanes for survelence and fighting, submarine warfare, machine guns and chemical warfare
The British code breaking group in Bletchley Park did.
Unrestricted submarine warfare is when submarines attach and sink other vessels (ships, freighters, tankers) without warning. Germany freely used unrestricted submarine warfare in WWI, and after that time, the rest of the world tried to have submarines abolished.
unrestricted submarine warfare
Germany violated the United States freedom of the seas during World War I with its unrestricted submarine warfare.
German submarine warfare
WW1 introduced submarine warfare, tanks, chemical warfare, and aerial combat. Man's history already knew battleship warfare from Tsushima in 1905; and massed land warfare consisting of infantry. WW2 REFINED submarine warfare, tanks, and aerial warfare; chemical warfare was outlawed by treaty.
Except for submarine warfare; naval warfare in WWI was not important. What engagements did occur, tipped the balance in neither direction.